Mobile rigs for drilling holes into the ground frequently employ a mast mounted on a support surface that is normally disposed parallel to the ground surface. A rotary power drill head for a drill pipe is mounted on the mast, and driven by a suitable source, such as a hydraulic power source. The rotary power drill head, in one configuration, is translatable along the mast, in the vertical direction, on a pair of chains extending vertically along the mast. During drilling, the power drill head is driven downwardly close to the ground surface; during drill pipe hoisting, the power drill head is raised, toward the top of the mast.
Drilling rigs of this nature have been employed to drill multiple holes into the ground at diverse sites. When it is desired to move the rig from one position to another, the mast is folded onto the vehicle and the vehicle is driven between sites.
Generally, such rigs have been employed in the past to drill blast holes and water wells. As such, depths have been generally restricted to 200 to 300 feet by employing no more than fifteen 20 to 25 foot long drill pipes, which when interconnected form a drill string. Attempts to use the prior art mobile rigs for deeper drilling generally fail because the weight of the drill pipe exceeds the load limit of the chains which support the rotary power drill head and the rotary power drill head cannot drive the drill pipe at sufficiently high speed. Also, it has frequently been necessary, in utilizing the mobile drilling rigs, to lay single lengths of pipe horizontally on the ground and to insert the single lengths of pipe into the rotary drill head. Such procedures are obviously time consuming, and therefore expensive.
While it has been the practice in oil field drilling to provide relatively immobile structures with extendable masts with a pipe racking platform, these practices have not been used for other terrain where the ground is harder than the sedimentary formations, where oil is usually located. Oil field equipment does not generally function adequately in hard, metamorphic volcanic rocks, as exist in hard rock mining areas, and in desert arid areas. In hard rock mining areas and arid desert areas there is a need, however, to drill relatively deep holes, such as 4,000 to 5,000 feet to obtain water. In addition, geothermal wells are frequently drilled to such a depth in hard rock mining and desert areas. It is also frequently desirable to drill deep holes in such areas for mineral exploration purposes. Oil well drilling also differs from hard rock drilling because in oil well drilling the drill pipe is turned by a rotary table that is fixedly mounted on the ground, and is not a part of the vehicle, as in the case of a power rotary drill head.
It is, therefore, an object of the present invention to provide a new and improved method of and apparatus for drilling relatively deep holes in various types of relatively hard substrata, for mining, blast hole, and quarry and/or water drilling purposes.
Another object of the invention is to provide a new and improved apparatus for and method of driving many lengths of drill pipe into the ground, and for hoisting sections of the drill pipe.